Author is likely incorrect about the C Corp retained earnings taxes, the tax owed for 100k of profit for Federal only would be more like $22,500 as the 15% rate is only for your first 50K of profit.

The corporate tax rate is very high and should really be thought of as 35% if you have meaningful profit.

You may also be able to defer profit if you're delivering service after you're paid for it (and you should be doing this), this keeps more money in the company without paying the taxes immediately. A far more important lesson.